Column 0 of square array A211970 (in which column 1 is A000041).

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =6a(5) =10a(6) =16a(7) =24a(8) =36a(9) =54a(10) =78a(11) =112a(12) =160a(13) =224a(14) =312a(15) =432a(16) =590a(17) =802a(18) =1084a(19) =1452a(20) =1936a(21) =2568a(22) =3384a(23) =4440a(24) =5800a(25) =7538a(26) =9758a(27) =12584a(28) =16160a(29) =20680